Color ink composition and color ink jet printing method

Abstract: A yellow ink composition, a magenta ink composition and cyan ink composition and a solvent system which are suitable for a color ink jet printing method are disclosed. These ink compositions can realize ideal color tones without limitation of properties of paper. Moreover, these ink compositions are excellent in intermittent jetting stability. The color ink jet printing method is also disclosed. In this method, ink compositions are overprinted to mix colors. Colors obtained by the color mixing Have an ideal color tone.

Description: BACKGROUND OF THE INVENTION Technical Field The present invention relates to an ink composition for use in color ink jet printing and more particularly to a yellow ink composition, a magenta ink composition, a solvent system suitable for a color ink composition and a color ink jet printing method using said ink compositions. Background Art In the "color ink jet printing method" wherein a color image is formed using an ink jet printing method, it is a common technique to use at least a yellow ink, a magenta ink and a cyan ink. In the color ink jet printing method, ink compositions for respective colors, as such, should first have a good color production property. In particular, it is preferred for a color to be faithfully produced even on plain paper, especially on acid paper. Furthermore, there is a color ink jet printing method wherein, in addition to three colors (yellow, magenta and cyan), four colors of red, green, blue and black are formed by overprinting the three color ink compositions, i.e., a yellow ink, a magenta ink and a cyan ink, to effect seven colors printing. (Black may be formed by over-printing yellow, magenta and cyan, or alternatively, a black ink may be used.) In this type of the color ink jet printing method, besides the good color production property of the ink compositions per se , it is important for the color ink compositions to produce faithful color tone of red, green and blue when mixed by overprinting. In general, an ink composition which has a good color production property when used alone cannot be expected to have a good color production property when mixed by overprinting. Furthermore, in many cases, even though a good colors can be realized on coated pater, a poor colors are produced on paper which has a high acidity. For this reason, there is a demand for ink compositions and combinations thereof that can realize the good color production when mixed by overprinting without limiting by properties of recording paper. Furthermore, the color ink composition for ink jet printing should have properties commonly required for ink jet printing, such as cause neither clogging of nozzles nor a change in composition and properties during storage. In particular, after a printing is suspended for a certain period, it is desirable that the printing start without any troubles such as the deviation of the ink droplets from the ink path and the missing of dots. It is preferable that the "suspending period" that is a period by the time when the deviation of the ink droplets or the missing of dots is observed should be long. An ink composition which has a long "suspending period" is hereinafter referred as an ink composition excellent in intermittent jetting stability. SUMMARY OF THE INVENTION The present inventors have now obtained several findings on ink compositions that can satisfy various properties required as an ink composition for color ink jet printing. The present invention has been made based on these findings. The object of the first aspect of the present invention is to provide an ink set comprising in combination a yellow ink composition, a magenta ink composition, and a cyan ink composition as defined in claim 1 having excellent color production property. The object of the second aspect of the present invention is to provide a color ink jet printing method that can realize a good color printed image using the above ink compositions. Accordingly, the yellow ink composition used according to the present invention comprises C.I.Direct Yellow 86 and C.I. Direct yellow 132 in a weight ratio of 1:3 to 3:1 and each in an amount of 0.3 to 3.0% by weight based on the ink composition. The magenta ink composition used according to the present invention comprises C.I. Acid Red 52 and C.I. Acid Red 289 in a weight ratio of 1:2 to 2:1 and each in an amount of 0.3 to 2.5% by weight based on the ink composition. The cyan ink composition used according to the present invention comprises 1 to 4% by weight of one or more dyes selected from a group consisting of C.I. Direct Blue 199, C.I. Direct Blue 86 and C.I. Acid Blue 9. The color ink jet printing method according to the second aspect of the present invention is a color ink jet printing method using an ink set comprising in combination a yellow ink composition, a magenta ink composition and a cyan ink composition as defined in claim 1. DETAILED DESCRIPTION OF THE INVENTION The yellow ink composition used according to the present invention comprises as dyes C.I.Direct Yellow 86 and C.I. Direct yellow 132 in a weight ratio of 1:3 to 3:1, preferably 1:2 to 2:1, and each in an amount of 0.3 to 3.0% by weight, preferably 0.5 to 2.0% by weight, based on the ink composition. The yellow ink composition of the present invention can realize ideal yellow. In particular, ideal color tone can be provided on plain paper, especially plain acid paper. If the amounts of the two dyes added are outside the respective ranges specified above, the yellow color tone may become reddish or greenish even when the yellow ink composition is used alone, so that no ideal yellow can be produced. Furthermore, when mixed with other color ink compositions by overprinting, no good production of red and green can be provided. There is also a possibility that a large difference in color production occurs between plain neutral paper and plain acid paper. Moreover, clogging is likely to occur in the recording head at its ejection port. The magenta ink composition used according to the present invention comprises as dyes C.I. Acid Red 52 and C.I. Acid Red 289 in a weight ratio of 1:2 to 2:1, preferably 2:3 to 3:2, and each in an amount of 0.3 to 3.5% by weight, preferably 0.5 to 2.5% by weight, based on the ink composition. The magenta ink composition of the present invention can realize ideal magenta. In particular, ideal color tone can be provided on plain paper, especially plain acid paper. If the amounts of the two dyes added are outside the respective ranges specified above, the color tone may become bluish or reddish even when the magenta ink composition is used alone, so that no ideal magenta can be provided. Furthermore, when mixed with other color ink compositions by overprinting, no good production of green and blue can be provided. There is also a possibility that a large difference in color production occurs between plain neutral paper and plain acid paper. Moreover, clogging is likely to occur in the recording head at its ejection port. Furthermore, the cyan ink composition used according to the present invention comprises 1 to 4% by weight, preferably 1.5 to 3.5% by weight, of one or more dyes selected from a group consisting of C.I. Direct Blue 199, C.I. Direct Blue 86 and C.I. Acid Blue 9. The cyan ink composition of the present invention can realize ideal color tone on plain paper, especially plain acid paper. There is no particular limitation on the solvent system for the yellow ink composition, the magenta ink composition and the cyan ink composition according to the present invention. However, it is preferred for the solvent system to contain an organic solvent and water capable of dissolving the dyes. Specific preferred examples of the organic solvent include amides, such as dimethylformamide and dimethylacetamide; ketones and keto-alcohols, such as acetone and diacetone alcohol; ethers, such as tetrahydrofuran and dioxane; alkylene glycols having 2 to 6 carbon atoms in their alkylene group, such as ethylene glycol, propylene glycol, triethylene glycol and diethylene glycol; glycerin; polyalkylene glycols, such as polyethylene glycol and polypropylene glycol; polyhydric alcohol lower monoalkyl ethers, such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether and triethylene glycol monomethyl (or ethyl) ether; polyhydric alcohol lower dialkyl ethers, such as triethylene glycol dimethyl (or ethyl) ether; alkyl alcohols having 1 to 5 carbon atoms, such as methyl alcohol, ethyl alcohol, n-propyl alcohol and n-butyl alcohol; and other organic solvents, such as sulfolane, pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and 1,5-pentanediol. These organic solvents may be used alone or in the form of a mixture of two or more of them. Various additives may be added as the third component to the ink compositions for the purpose of improving various properties. For example, in order to adjust various properties, such as viscosity, surface tension, pH and specific resistance, or to prevent putrefaction and mildew, it is possible to add anionic surfactants, such as fatty acid salts, salts of alkylsulfates, alkylbenzenesulfonic acids and salts of alkylnaphthalenesulfonic acid; nonionic surfactants, such as acetylene glycols, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters and sorbitan fatty acid esters; water-soluble naturally occurring or synthetic polymers, such as celluloses, polyvinyl-pyrrolidone, polyvinyl alcohol and water-soluble resins; amines, such as diethanolamine and triethanolamine; and inorganic salts, such as lithium chloride, ammonium chloride and sodium chloride. Examples of the coloring component of the ink usable in the present invention include direct dyes, acidic dyes, food dyes, basic dyes, reactive dyes, disperse dyes, vat dyes, soluble vat dyes, reactive disperse dyes and oil dyes. Water-soluble dyes are preferably used from the viewpoint of performance of the recording solution, and particularly preferred examples thereof include: C.I. Direct Red 2, 4, 9, 23, 26, 31, 39, 62, 63, 72, 75, 76, 79, 80, 81, 83, 84, 89, 92, 95, 111, 173, 184, 207, 211, 212, 214, 218, 221, 223, 224, 225, 226, 227, 232, 233, 240, 241, 242, 243 and 247; C.I. Direct violet 7, 9, 47, 48, 51, 66, 90, 93, 94, 95, 98, 100 and 101; C.I. Direct Yellow 8, 9, 11, 12, 27, 28, 29, 33, 35, 39, 41, 44, 50, 53, 58, 59, 68, 86, 87, 93, 95, 96, 98, 100, 106, 108, 109, 110, 130, 132, 142, 144, 161 and 163; C.I. Direct Blue 1, 10, 15, 22, 25, 55, 67, 68, 71, 76, 77, 78, 80, 84, 86, 87, 90, 98, 106, 108, 109, 151, 156, 158, 159, 160, 168, 189, 192, 193, 194, 199, 200, 201, 202, 203, 207, 211, 213, 214, 218, 225, 229, 236, 237, 244, 248, 249, 251, 252, 264, 270, 280, 288, 289 and 291; C.I. Direct Black 9, 17, 19, 22, 32, 51, 56, 62, 69, 77, 80, 91, 94, 97, 108, 112, 113, 114, 117, 118, 121, 122, 125, 132, 146, 154, 166, 168, 173 and 199; C.I. Acid Red 35, 42, 52, 57, 62, 80, 82, 111, 114, 118, 119, 127, 128, 131, 143, 151, 154, 158, 249, 254, 257, 261, 263, 266, 289, 299, 301, 305, 336, 337, 361, 396 and 397; C.I. Acid violet 5, 34, 43, 47, 48, 90, 103 and 126; C.I. Acid Yellow 17, 19, 23, 25, 39, 40, 42, 44, 49, 50, 61, 64, 76, 79, 110, 127, 135, 143, 151, 159, 169, 174, 190, 195, 196, 197, 199, 218, 219, 222 and 227; C.I. Acid Blue 9, 25, 40, 41, 62, 72, 76, 78, 80, 82, 92, 106, 112, 113, 120, 127:1, 129, 138, 143, 175, 181, 205, 207, 220, 221, 230, 232, 247, 258, 260, 264, 271, 277, 278, 279, 280, 288, 290 and 326; C.I. Acid Black 7, 24, 29, 48, 52:1 and 172; C.I. Reactive Red 3, 13, 17, 19, 21, 22, 23, 24, 29, 35, 37, 40, 41, 43, 45, 49 and 55; C.I. Reactive Violet 1, 3, 4, 5, 6, 7, 8, 9, 16, 17, 22, 23, 24, 26, 27, 33 and 34; C.I. Reactive Yellow 2, 3, 13, 14, 15, 17, 18, 23, 24, 25, 26, 27, 29, 35, 37, 41 and 42; C.I. Reactive Blue 2, 3, 5, 8, 10, 13, 14, 15, 17, 18, 19, 21, 25, 26, 27, 28, 29 and 38; C.I. Reactive Black 4, 5, 8, 14, 21, 23, 26, 31, 32 and 34; C.I. Basic Red 12, 13, 14, 15, 18, 22, 23, 24, 25, 27, 29, 35, 36, 38, 39, 45 and 46; C.I. Basic Violet 1, 2, 3, 7, 10, 15, 16, 20, 21, 25, 27, 28, 35, 37, 39, 40 and 48; C.I. Basic Yellow 1, 2, 4, 11, 13, 14, 15, 19, 21, 23, 24, 25, 28, 29, 32, 36, 39 and 40; C.I. Basic Blue 1, 3, 5, 7, 9, 22, 26, 41, 45, 46, 47, 54, 57, 60, 62, 65, 66, 69 and 71; and C.I. Basic Black 8. The amount of these dyes added is determined depending upon, for example, the kind of dyes, the kind of the solvent component, the properties required of the ink. It is generally in the range of from 0.2 to 15% by weight, preferably in the range of from 0.5 to 10% by weight based on the total weight of the ink. In the present invention, high-boiling, low-volatile, polyhydric alcohols, such as glycerin, ethylene glycol, diethylene, glycol, triethylene glycol, propylene glycol, dipropylene glycol, hexylene glycol, polyethylene glycol and polypropylene glycol, may be used as the hydrophilic, high-boiling, low-volatile solvent, and other water-soluble organic solvents including nitrogen-containing organic solvents, such as N-methyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, monoethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, diethanolamine, N-n-butyldiethanolamine, triisopropanolamine and triethanolamine, may be added thereto in such an amount as will give rise to no bleeding in the print. Diethylene glycol and glycerin are especially preferred. These hydrophilic, high-boiling, low-volatile solvents are known to be added as a humectant for preventing clogging. The addition of the hydrophilic, high-boiling, low-volatile solvent as an essential component in the present invention also may play a role in alleviating the corrosion of the members. When volatile components, such as water, are evaporated within the head or the ink passage due to occurrence of an accident, such as malfunction of the printing device, the hydrophilic, high-boiling, low-volatile solvent alleviates the corrosion of the members by the polyhydric alcohol lower alkyl ether. According to a preferred embodiment of the present invention, it is preferred for the ink composition to further comprise benzotriazole. The addition of benzotriazole is advantageous for a printer system in which the ink composition is fed from the ink vessel to the recording head-and an ink absorber is placed within the ink vessel so as for the ink composition to be held therein through absorption and impregnation into the ink absorber. Porous foams, such as urethane foam, have been generally used as the ink absorber to be placed within the ink vessel. From these absorbers, catalysts, foaming agents, foam stabilizers and other additives used during the production of porous foams are sometimes eluted into the ink composition. These eluted components are likely to cause a change in properties of the ink (for example, a high tendency for foaming or a change in contact angle). These components are also likely to change the properties of the ink passage or the surface of the nozzle, which is detrimental to jetting stability of ink droplets. These phenomena can be effectively prevented by adding benzotriazole to the ink composition. The recording head in which the nozzle surface has been treated to have water repellent property is sometimes employed for stably jetting ink droplets. For example, eutectoid plating using a nickel-fluoropolymer is generally utilized for the water-repellent treatment (For example, the treatment according to the method described in EP-A-0506128 is preferably employed. This water-repellent treatment is obtained by electroplating an electroformed nickel plate having nozzles in a nickel plating solution in which polytetrafluoroethylene is dispersed in concentration of about 20%.) A deterioration in water repellency imparted by the water-repellent treatment may be accelerated by the polyhydric alcohol lower alkyl ether, acetylene glycol. Addition of benzotriazole is advantageous also in that the deterioration in the water repellency of the nozzle surface can be effectively prevented. The ink jet printing method according to the second aspect of the present invention comprises effecting color ink jet printing using a combination of a yellow ink, a magenta ink and a composition as defined in claim 1 cyan ink. In the present invention, although any color ink jet printing technique may be used, it is especially preferred to use a printing technique using seven colors in total wherein three color ink compositions of yellow, magenta and cyan are used, any two of the yellow ink, the magenta ink and the cyan ink are overprinted to form red, green and blue, and black is formed by overprinting the three colors or alternatively a black ink is used. The yellow ink, the magenta ink and the cyan ink realize excellent ideal colors. Furthermore, overprinting of any two of these ink compositions can realize red, green and blue having nearly ideal color tones without depending on the properties of recording paper. Specifically, red provided by overprinting the yellow ink and the magenta ink, green provided by over printing the yellow ink and the cyan ink and blue provided by overprinting the magenta ink and the cyan ink can be produced in nearly ideal color tones on various kinds of recording paper, for example, plain recording paper having a high acidity. This means that good colors can be provided independently of the recording materials. According to a preferred embodiment of the present invention, the amounts of yellow ink, magenta ink and cyan ink jetted through nozzles of a printing head as droplet may be the same in the formation of red, green and blue. In general, in overprinting of the ink compositions, in theory, color tones of red, green and blue can be regulated by adjusting the amounts of the yellow, magenta and cyan ink compositions jetted through the nozzles. This technique, however, is complicated and disadvantageous from the practical point of view. Specifically, differentiation in the amount of the yellow ink jetted between the formation of red and formation of green is disadvantageous from the practical viewpoint. The present invention is advantageous, because red, green and blue can be produced in good color tones with the amounts of yellow, magenta and cyan inks jetted being kept constant. Various properties of the ink compositions, especially the ink composition according to the fourth aspect of the present invention, are determined by the compositions of the inks and also can be properly determined by taking several requirements into consideration. For example, the surface tension is preferably 29 mN/m or more. EXAMPLES The present invention will now be described in more detail with reference to the following Examples, though it is not limited to these Examples only. In the following Example, "%" is by weight. Reference Example A The following yellow ink compositions were prepared. Reference Example A1 C.I. Direct Yellow 86 0.3 % C.I. Direct Yellow 132 (Weight ratio = 1:3) 0.9 % Glycerin 5 % Water Balance Reference Example A2 C.I. Direct Yellow 86 1 % C.I. Direct Yellow 132 (Weight ratio = 1:2) 2 % Ethylene glycol 10 % Surfynol 465 1 % Water Balance Reference Example A3 C.I. Direct Yellow 86 1 % C.I. Direct Yellow 132 1 % (Weight ratio = 1:1) Glycerin 5 % Ethylene glycol 5 % Water Balance Reference Example A4 C.I. Direct Yellow 86 2 % C.I. Direct Yellow 132 3% (Weight ratio = 2:3) Glycerin 5 % Diethylene glycol 10% Water Balance Reference Example A5 C.I. Direct Yellow 86 3 % C.I. Direct Yellow 132 (Weight ratio = 3:1) 1 % Glycerin 5 % Polyethylene glycol #200 5 % Water Balance Comparative Example A1 C.I. Direct Yellow 86 2 % Glycerin 5 % Water Balance Comparative Example A2 C.I. Direct Yellow 132 2 % Diethylene glycol 10 % Water Balance Comparative Example A3 C.I. Direct Yellow 86 0.2 % C.I. Direct Yellow 132 0.2 % Glycerin 5 % Diethylene glycol 5 % Surfynol 465 1 % Water Balance Comparative Example A4 C.I. Direct Yellow 86 4 % C.I. Direct Yellow 132 1 % Polyethylene glycol #200 10 % Water Balance Comparative Example A5 C.I. Direct Yellow 86 4 % C.I. Direct Yellow 132 4 % Glycerin 5 % Ethylene glycol 5 % Surfynol 465 1 % Water Balance The ink compositions were prepared by mixing the above ingredients together, stirring the mixture at 60°C for 2 hr to dissolve the ingredients and filtering the solution through a membrane filter having a diameter of 0.8 µm under a pressure of 2 kg/cm 2 . Evaluation Test A The yellow ink compositions prepared in Reference Examples A1 to A5 and Comparative Examples A1 to A5 were evaluated as follows. Printing was performed using an experimental 48-nozzle ink jet printer under conditions of a jetting nozzle diameter of 30 µm, a piezoelectric element drive voltage of 80 V, a drive frequency of 3 kHz, a resolution of 360 dots/inch and an amount of ink jetted of 0.08 µg/dot. Evaluation A1: Color production (coated paper) A 100%-duty print image (3 x 3 cm) was formed on an ink jet printing paper having a coat layer (IJ Mattcoat NM manufactured by Mitsubishi Paper Mills, Ltd.) using various yellow inks. With respect to the yellow color production, in the print image, the L*a*b* color specification system in the color difference indication method specified in CIE (Commission Internationale de I'Eclairage) was measured with a Macbeth CE-7000 spectrophotometer (manufactured by Macbeth), and the color difference between the measured value and the yellow color tone standard value (L* = 90.7, a* = -18.8, b* = 91.1) of ISO 2845-1975 was determined by the following equation (I): ΔE*ab = [(ΔL*) 2 + (Δa*) 2 + (Δb*) 2 ] 1/2 The color differences were as given in Table 1. In the table, the color difference ΔE*ab was evaluated based on the following criteria: Color difference E*ab: Less than 5 - good (○) Not less than 5 - poor (x) Evaluation A2: Color production (plain paper, neutral paper and acid paper) A 100%-duty print image was formed on the following plain paper (neutral paper and acid paper) as described in Evaluation A1. Recording paper used for evaluation: Xerox-R (neutral paper manufactured by Fuji Xerox Co., Ltd.) Neenath bond (25% cotton fiber (acid paper) manufactured by Neenah bond) Canon Dry (acid paper manufactured by Canon Sales Co., Ltd.) EPP (acid paper manufactured by Seiko Epson Corporation) Xerox 4024 3R721 (acid paper manufactured by Xerox) Conqueror (100 g/m 2 ) (neutral paper manufactured by Arjo Wiggin.) The color tones of the solid printing was evaluated in the same manner as that of Evaluation A1, except that the color difference was determined based on printing image on Xerox-P paper. The color difference and the evaluation were as given in Table 1. Evaluation A3: Jetting stability (clogging of nozzle) Printing operation was carried out using each yellow ink composition to confirm that ink droplets were projected from all the nozzles. Thereafter, the printer was allowed to stand in a temperature environment of 40°C without cap-ping the recording head. After one month, the printing operation was resumed to observe the printing state. Normal printing could be carried out immediately after resumption or after cleaning operation was repeated 3 times or less - good (○); Normal printing could be carried out after cleaning operation was repeated 4 to 10 times - slightly poor (Δ); and Normal printing could be carried out after cleaning operation was repeated not less than 11 times, or no normal printing could be carried out even after repeated cleaning operation - poor (X). Reference Example B The following magenta ink compositions were prepared. Reference Example B1 C.I. Acid Red 52 0.3 % C.I. Acid Red 289 0.6 % Diethylene glycol 20 % Proxel XL2 (Preservative manufactured by ZENECA) 0.5 % Water Balance Reference Example B2 C.I. Acid Red 52 1 % C.I. Acid Red 289 2 % Diethylene glycol 10 % Glycerin 13 % Proxel XL2 0.5 % Water Balance Reference Example B3 C.I. Acid Red 52 1 % C.I. Acid Red 289 1 % Diethylene glycol 15 % Surfynol 465 1 % Proxel XL2 0.5 % Water Balance Reference Example B4 C.I. Acid Red 52 2.5 % C.I. Acid Red 289 1.3 % Glycerin 15 % Polyethylene glycol (#200) 10 % Proxel XL2 0.5 % Water Balance Reference Example B5 C.I. Acid Red 52 0.9 % C.I. Acid Red 289 0.6 % Diethylene glycol 15 % Triethylene glycol monobutyl ether 10 % Proxel XL2 0.3 % Water Balance Reference Example B6 C.I. Acid Red 52 0.9 % C.I. Acid Red 289 0.7 % Glycerin 10 % Triethylene glycol 10 % Surfynol 465 1.5 % Proxel XL2 0.3 % Water Balance Reference Example B7 C.I. Acid Red 52 1.2 % C.I. Acid Red 289 0.8 % Glycerin 10 % Diethylene glycol 5 % Triethylene glycol monobutyl ether 10 % Proxel XL2 0.5 % Water Balance Reference Example B8 C.I. Acid Red 52 0.7 % C.I. Acid Red 289 0.7% Glycerin 15 % Polyethylene glycol (%200) 10% Proxel XL2 0.3 % Water Balance Comparative Example B1 C.I. Acid Red 52 2 % Glycerin 15 % Proxel XL2 0.5 % Water Balance Comparative Example B2 C.I. Acid Red 289 2 % Diethylene glycol 20 % Proxel XL2 0.3 % Water Balance Comparative Example B3 C.I. Acid Red 52 0.2 % C.I. Acid Red 289 0.2 % Glycerin 10 % Diethylene glycol 15 % Proxel XL2 0.5 % Water Balance Comparative Example B4 C.I. Acid Red 52 0.5 % C.I. Acid Red 289 2 % Glycerin 10 % Polytriethylene glycol (#200) 15 % Proxel XL2 0.5 % Water Balance Comparative Example B5 C.I. Acid Red 52 3 % C.I. Acid Red 289 3 % Glycerin 10 % Triethylene glycol 15 % Proxel XL2 0.3 % Water Balance The ink compositions were prepared by mixing the above ingredients together, stirring the mixture at 70°C for 2 hr to dissolve the ingredients and filtering the solution through a membrane filter having a diameter of 0.8 µm under a pressure of 2 kg/cm 2 . Evaluation Test B The magenta ink compositions prepared in Reference Examples B1 to B5 and Comparative Examples B1 to B5 were evaluated as follows. Printing was carried out using an experimental 48-nozzle ink jet printer under conditions of a jetting nozzle diameter of 30 µm, a piezoelectric element drive voltage of 25 V, a drive frequency of 5 kHz, a resolution of 360 dots/inch and an amount of ink jetted of 0.05 µg/dot. Evaluation B1: Color production A 100%-duty print image (3 x 3 cm) was formed on the following plain paper using each magenta ink composition. Recording paper used for evaluation: Neenah Bond (acid paper manufactured by Kimberly-Clark) Xerox-P (neutral paper manufactured by Fuji Xerox Co., Ltd.) Canon Dry (acid paper manufactured by Canon Sales Co., Ltd.) Yamayuri (acid paper manufactured by Honshu Paper Co., Ltd.) Ricopy 6200 (acid paper manufactured by Ricoh Co., Ltd.) EPP (acid paper manufactured by Seiko Epson Corporation) Xerox R (acid paper manufactured by Fuji Xerox Co., Ltd.) Xerox 4024 3R721 (acid paper manufactured by Xerox Co.) Conqueror (100 g/m 2 ) (neutral paper manufactured by Arjo Wigging) Rapid Copy (neutral paper manufactured by Igepa Plus) Mode White Copy 80 (neutral paper manufactured by Modo) The color production of the solid prints was evaluated in terms of the color difference between the measured value and the magenta color tone standard value (L*=48.4, a*=78.1, b*=-7.1) specified in ISO 2845-1975 in the same manner as that of the evaluation A1. The resultant color differences were as given in Table 2. In the table, the color difference ΔE*ab was evaluated based on the following criteria. ΔE*ab was less than 2 for all the types of recording paper - excellent (o ○); ΔE*ab was in the range of from 2 to less than 3 for at least one type of recording paper, or the average ΔE*ab value of the measured values for all the types of recording paper was in the range of from 2 to less than 3 - good (○); and ΔE*ab was 3 or more for at least one type of recording paper, or the average ΔE*ab value of the measured values for all the types of recording paper was 3 or more - poor (X). Evaluation B2 : Several solid prints prepared in Evaluation B1 were evaluated in the same manner as that of Evaluation B1, except that the color difference was determined based on a print on Xerox-P paper. The color difference and the evaluation were as given in Table 2. Evaluation B3: Jetting stability (clogging of nozzle) Each magenta ink composition was evaluated on the jetting stability in the same manner as that of Evaluation A3. The results were as given in Table 2. Evaluation B4: Jetting stability (long-term continuous recording) Printing was carried out continuously for 48 hr using each magenta ink composition under temperature environments of 5°C, 20°C and 40°C. The printing state was evaluated as follows: No dropout of dots was observed at all the temperatures with stable printing - good (○); Dropout of dots was observed with elapse of time at any one of the temperatures - slightly poor (Δ); and Dropout of dots was observed from early stage of printing at any one of the temperatures - poor (X). Example C Combinations of color ink compositions comprising a black ink, a yellow ink, a magenta ink and a cyan ink (Reference Examples C1, C3 to C5, C7, C8 and C11 to C14, and Examples C2, C6, C9 and C10) as specified in Table 3 and combinations of color ink compositions (Comparative Examples C15 to C18 and C20 to C22, and Example C19 as specified in Table 4 were provided. In the tables, B, Y, M and C respectively represent black, yellow, magenta and cyan ink compositions, TEG-mBE represents triethylene glycol monobutyl ether, and DEG-mBE represents diethylene glycol monobutyl ether. The resultant ink compositions were subjected to measurement of surface tension. The measured values were as given in the tables. Evaluation C The above ink compositions were evaluated as follows. Printing was carried out using an experimental 48-nozzle ink jet printer under conditions of a jetting nozzle diameter of 30 µm, a piezoelectric element drive voltage of 20 V, a drive frequency of 5.5 kHz, a resolution of 360 dots/inch and an amount of ink jetted of 0.05 µg/dot. PPC paper (PPC paper manufactured by Xerox Corp. and RICOPY 6200 manufactured by Ricoh Co., Ltd.), regenerated paper (Yamayuri manufactured by Honshu Paper Co., Ltd.), bond paper (Gilbert Bond 25% cotton paper manufactured by Mead Corp.) and wood-free paper (OK wood-free paper L manufactured by Oji Paper Co., Ltd.) were used as the recording paper. Evaluation C1: Quick drying A 100%-duty printing of a single color was formed using each color ink composition. A 100%-duty printing of a combination of two ink compositions was further carried out by overprinting. After elapse of predetermined period of time from printing, paper of the same type as the recording paper used for printing was overlaid on the print with a pressure of 200 g/cm 2 to observe whether or not migration of ink occurred between the two sheets of paper. The results were evaluated as follows. The results of evaluation were as given in Table 5. No ink migration was observed even within less than 1 sec from printing for all prints - excellent (o ○); No ink migration became not observed 1 to 2 sec after printing for all the prints - good (○); No ink migration became not observed 2 to 5 sec after printing for all the prints -slightly poor (Δ); and Ink migration was observed even after elapse of 5 sec or longer from printing for any one of the prints - poor (X). Evaluation C2: Quality of single-color print Alphabets were printed using each color ink composition. Observation was made on the occurrence of bleeding and feathering of prints. The results were evaluated as follows. The results of evaluation were as given in Table 5. Neither bleeding nor feathering was substantially observed - excellent (o ○); Bleeding and/or feathering were somewhat observed in some types of paper - good ○); Bleeding and/or feathering were observed in some types of paper - slightly poor (Δ); and Bleeding and/or feathering were observed in all the types of paper - poor (X). Evaluation C3: Quality of color mixing print A 100%-duty printing of one color ink composition among four color ink compositions was formed. Then, a 100%-duty printing of other color ink composition was formed so as to contact with the 100%-duty printing previously formed. The boundary portion was observed with the naked eye. The results were evaluated as follows. The results of observation was as given in Table 5. Neither bleeding nor feathering derived from color mixing was substantially observed in all the combinations - excellent (o ○); Bleeding and/or feathering derived from color mixing were somewhat observed in some combinations - good (○); Bleeding and/or feathering derived from color mixing were observed in some combinations depending upon types of paper - slightly poor (Δ); and Bleeding and/or feathering derived from color mixing were observed in all the types of paper - poor (X). Evaluation C4: Jetting stability Printing was continuously carried out using each color ink composition, and the time taken for dropout of dots and scattering of ink to be observed ten times in total was measured. The results were evaluated as follows. The results of evaluation were as given in Table 5. Successful printing for 48 hr or longer for all the ink compositions - excellent (o ○); Successful printing for 24 to 48 hr for any one of the color ink compositions - good (○); Successful printing for 1 to 24 hr for any one of the color ink compositions - slightly poor (Δ); and Successful printing for shorter than 1 hr for any one of the color ink compositions - poor (X). Evaluation C5: High-speed response The jetting stability in a high-speed response was evaluated in the same manner as that of Evaluation C3, except that the drive frequency of the recording head was 10 kHz. The results were as given in Table 5. Evaluation C6: Intermittent jetting stability Printing of a line was performed using each color ink composition under the condition of 25°C and 20% humidity, suspended for a predetermined period and the resumed. Observation was made on the occurrence of dropout or deviation from ink path of the first dot when the printing was resumed. The suspending period by the time when dropout or deviation from ink path was observed was evaluated as follows. The results of evaluation were as given in Table 5. Over 60 seconds - excellent (1) 50 to 60 seconds - excellent (2) 30 to 40 seconds - excellent (3) 20 to 10 seconds - good (○) 5 to 10 seconds - slightly poor (Δ) less then 5 seconds - poor (X). Evaluation C7: Corrosion of member by ink composition Head members and members for feeding and discharging (specifically, ABS, AS, PS, PP, PSF, PC, PE, PET, PBT, nylon, ACS, POM, butyl rubber, silicone rubber, fluoro rubber, and EPDM rubber), which are likely to contact with the ink, were immersed in each color ink and allowed to stand at 25°C for 3 months. Then, a change in weight and appearance were observed. The results were evaluated as follows. The results of evaluation were as given in Table 5. Each member exhibited a weight change within 5% with substantially no change in appearance - excellent (o ○); Each member exhibited a weight change within 10% with substantially no change in appearance - good (○); Each member exhibited a weight change exceeding 10% with substantially no change in appearance - slightly poor (Δ); and Each member exhibited a weight change exceeding 10% and swelling and dissolution - poor (X). Example D Dyes in Table 6 and other ingredients specified were mixed together to provide ink compositions and the combination thereof as Examples D1 to D4 and Comparative Examples D1 to D5. Examples D1 to D4 and Comparative Examples D1 to D5 Dye Amount specified in Table 6 Glycerin 5 % Diethylene glycol 10 % Surfynol 465 1 % Pure water Balance Examples D5 and D6 Dye Amount specified in Table 6 Triethylene glycol monobutyl ether 17 % Diethylene glycol 10 % Surfynol 465 0.8 % Pure water Balance Yellow Ink Magenta Ink Cyan Ink D.B.199 D.Y.86 D.Y.132 A.R.52 A.R.289 Example 1 0.3 0.9 0.3 0.6 1 2 1 2 1 2 3 3 1 1 1 1 2 4 2 3 2.5 1.3 4 5 3 1 0.9 0.6 2.5 6 0.5 0.5 0.9 0.7 1.5 7 1 0.75 1.2 0.8 3.5 8 0.5 0.75 0.7 0.7 2.5 Comparative Example 1 1 1 1 1 5 2 1 1 2 - 2 3 1 1 - 2 2 4 1 - 1 1 2 5 - 2 1 1 2 Evaluation D These ink compositions were evaluated as follows. (1) Evaluating printer An ink jet printing printer provided with an ink jet printing head having 48 nozzles, which printer permits printing under conditions of a jetting nozzle diameter of 30 µm, a piezoelectric element drive voltage of 25 V, a drive frequency of 5 kHz, a resolution of 360 dots/inch and an amount of ink jetted of 0.05 µg/dot. (2) Recording paper used for evaluation Xerox-R (manufactured by Fuji Xerox Co., Ltd.) Neenah bond (25% cotton fiber manufactured by Neenah bond) Canon Dry (Canon Sales Co., Ltd.) EPP (Epson Hanbai Corp.) Xerox 4024 3R721 (manufactured by Xerox Corp.) (3) Evaluation method A 100%-duty printing of red, green and blue was carried out using combinations of ink compositions of the Examples and Comparative Examples. Specifically, 100%-duty printing of red was carried out by overprinting the yellow ink and the magenta ink, sold printing of green was carried out by overprinting the yellow ink and the cyan ink, and solid printing of blue was carried out by overprinting the magenta ink and the cyan ink. In order to evaluate the color tones with respect to the 100%-duty print image (3 x 3 cm), the L*a*b* color specification system in the color difference indication method specified in CIE (Commission International de I'Eclairage) was measured with a Macbeth CE-7000 spectrophotometer (manufactured by Macbeth), and the color difference between the measured value and the color tone standard value of ISO 2845-1975 given in Table 7 was determined by the following equation (I). L* a* b* Red 47.4 70.3 47.5 Green 47.6 -74.1 23.2 Blue 19.2 35.5 -53.0 ΔE*ab = [(ΔL*) 2 + (Δa*) 2 + (Δb*) 2 ] 1/2 The color differences were as given in Table 8. In the table, the color difference E*ab was evaluated based on the following criteria. Color difference E*ab for the three colors: 20 or less for all the colors - excellent (o ○); More than 20 to 30 for any one of the colors - good (○); More than 30 for any one of the colors - poor (X). ΔE*ab Red Green Blue Evaluation Example 21.0 17.5 26.5 ○ 2 23.2 19.1 18.6 ○ 3 18.8 19.7 19.3 o ○ 4 24.7 25.8 28.7 ○ 5 18.0 16.2 13.0 o ○ 6 15.2 17.6 12.4 o ○ 7 19.4 14.4 16.7 o ○ 8 18.1 19.2 17.1 o ○ Comparative Example 18.8 45.0 33.8 × 2 41.2 19.7 39.3 × 3 42.3 19.7 38.8 × 4 45.1 32.5 19.3 × 5 40.9 36.3 19.3 ×

Claims: An ink set comprising, in combination (i) a yellow ink composition comprising C.I. Direct Yellow 86 and C.I. Direct Yellow 132 in a weight ratio of 1:3 to 3:1 and each in an amount of 0.3 to 3.0% by weight based on the ink composition; (ii) a magenta ink composition comprising C.I. Acid Red 52 and C.I. Acid Red 289 in a weight ratio of 1:2 to 2:1 and each in an amount of 0.3 to 2.5% by weight based on the ink composition; and (iii) a cyan ink composition comprising 1 to 4% by weight of one or more dyes selected from a group consisting of C.I. Direct Blue 199, C.I. Direct Blue 86 and C.I. Acid Blue 9. An ink cartridge comprising an ink set according to claim 1, wherein the ink compositions (i), (ii) and (iii) are contained in separated spaces in the cartridge, respectively. A color ink jet printing method using a yellow ink composition (i) as defined in claim 1, a magenta ink composition (ii) as defined in claim 1 and a cyan ink composition as defined in claim 1. The method according to claim 3, wherein any two of the yellow ink composition (i), the magenta ink composition (ii) and the cyan ink composition (iii) are overprinted to form red, green and blue for color printing. The method according to claim 3, wherein acid paper is used as recording paper.

Inventors: HAYASHI HIROKO, ITANO MASAAKI, KOIKE YOSHIYUKI, KUBOTA KAZUHIDE, OHNISHI HIROYUKI, TAKEMOTO KIYOHIKO, YOSHIDA MIHARU, YOSHIIKE ETSUKO, HAYASHI, HIROKO, ITANO, MASAAKI, KOIKE, YOSHIYUKI, KUBOTA, KAZUHIDE, OHNISHI, HIROYUKI, TAKEMOTO, KIYOHIKO, YOSHIDA, MIHARU, YOSHIIKE, ETSUKO
Applicants: SEIKO EPSON CORP, SEIKO EPSON CORPORATION
Application year: 1994
Main classification: C09D11
IPC codes: C09D11